In the known longitudinally arranged baking ovens for the production of thin-walled shaped bodies from shapeless masses, for the production of shaped bodies opening and closing mold halves are contained in 18 to 140 opening and closing baking tongs, whereby each mold with both its mold halves is received in the two tong halves of a baking tongs. The baking tongs are connected in an endless chain, which runs continuously through the antechamber and subsequent baking space of the respective baking oven in one direction. When passing through the antechamber, the baking tongs are opened to open of their baking molds, first in order to remove the respective thin-walled shaped body from the open baking mold, and then to introduce a measured amount of the shapeless mass into the opened baking mold. Subsequently the baking tongs are closed to close its baking mold. During the subsequent passage through the oven, the baking molds are heated and each shapeless mass enclosed in the closed baking molds is baked into a thin-walled shaped body, while the baking molds are kept closed against the inner pressure generated inside them during baking.
In these baking ovens the longitudinally extending endless baking tong chain is arranged in two superimposed transport levels through the respective longitudinally extending baking space, and is guided from the one transport level to the other transport level at the rear end of the baking space and at the front end of the antechamber frontally connected to the baking space.
Each baking tong is designed as an externally actuatable machine, by means of which the therein contained baking mold is transported through the baking oven, opened and closed and kept closed. When passing through the antechamber, the baking mold is opened by means of its baking tongs, kept open for a short time and then closed again. When passing through the baking space, the closed baking mold is kept closed by means of its baking tong. The endless baking tong chain is driven by a driving motor, which produces a continuous revolving motion of the baking tong chain. Because of this continuouse motion each baking tong is subjected to the same motion sequence. When in the antechamber they pass the respectively assigned control mechanisms, stationarily arranged in the antechamber, which in connection with the revolving motion of the baking tong chain produce each time the respective motion sequence of the baking tongs, or of its parts.
When running though the antechamber the open baking tongs pass the product removal station, wherein the baked shaped bodies are removed from the opened baking molds and are discharged from the antechamber via the discharge station of the oven. After the product removal station, the opened baking tongs pass the loading station, wherein the measured amount portions of the shapeless mass are introduced into the empty, open baking molds. During its travel through the longitudinally extending, horizontal baking space of the oven, the closed molds are heated in the closed baking tongs. In a gas-heated oven the baking molds are heated from the outside with hot gases, which are generated in the baking space of the oven and directed towards the baking tongs. In an electrically heated oven the baking molds are heated by means of the electric heating elements built into the tong halves of the baking tongs, which during their travel through the baking space are supplied with electric energy from an external source.
The thin-walled shaped bodies are produced in successive cycles, in the baking molds transported in cycle through the baking space by the baking tongs. Each baking cycle takes place in the respective baking mold during its travel from the loading station through the baking space to the product removal station. In each single baking cycle, in the loading station a shapeless mass is introduced into the baking mold previously opened by its baking tongs, the baking mold is closed and kept closed by means of its baking tongs, until it is opened again by means of its baking tong before it reaches the product removal station, and the thin-walled shaped body is removed from the open baking mold.
When the open baking mold is again transported by its baking tongs to the loading station, then in this baking mold starts the next baking cycle for the production of a thin-walled shaped body.
In each baking cycle, during the baking process in the mold kept closed from the outside by the baking tongs, the shapeless mass enclosed in the closed baking mold is distributed, foamed up and baked under pressure into a foamed, thin-walled shaped body. The outer configuration of the resulting thin-walled shaped body is determined on its upper side by the surface configuration of the baking surface of the upper mold half and on its underside by the surface configuration of the baking surface of the lower mold half of the baking mold. The wall thickness of the resulting thin-walled shaped body is determined by the distance between these two mutually facing baking surfaces, when the mold is closed. The contour of the outer border of the resulting thin-walled shaped body is determined by the lateral limits of the hollow mold space of the closed baking mold.
When the baking mold and the baking tong are closed, the two tong halves and the two mold halves lie opposite to each other. The tong halves are supported against each other by means of assigned mutually opposite stops. The baking surfaces arranged on the frontal side of the baking molds are faced each other and are opposite to each other at a predetermined distance. These two substantially horizontally arranged baking surfaces define between them the hollow mold space of the closed baking mold which, depending on the product to be made in the baking mold into a thin-walled shaped body, is laterally open, or laterally limited all around by sealing strips, but not closed up to be gastight. In this hollow mold space a measured amount of the shapeless mass is baked under pressure into a thin-walled shaped body. The baking gases formed during baking in the hollow mold space cause the foaming of the shapeless mass, distribute it throughout the hollow mold space and flow out laterally from the hollow mold space of the closed baking mold, between the two baking surfaces, into the baking space of the respective baking oven. When the baking mold and the baking tong are closed, the baking gases create an inner pressure in the hollow mold space of the baking mold, which is transmitted via the baking surfaces to the mold halves and from these to the tong halves of the baking tongs. This inner pressure is counteracted by the closed baking tongs, which during their revolution, depending on the baking tong and the baking mold, are kept closed either by the inherent weight of their tong halves, or by stationary closing means acting from the outside, or due to baking tong locks laterally mounted on their tong halves, thereby preventing their tong halves lying against each other with their stops from being moved apart by the baking gases.
The inner pressure produced by the baking gases increases in the initial phase of the baking process due to the very intense gas development and decreases with the progressive escape of the baking gases from the hollow mold space. The thereby occurring pressure maximum of the inner pressure depends mainly on the design of the lateral limitation of the hollow mold space, and is therefore considerably lower in a hollow mold space which is completely open laterally than in a hollow mold space which is bordered all around by sealing strips and wherefrom the gases can leave only through a few steam slots of the sealing strips.
In the case of a baking tong whose articulately joined tong halves contain a baking mold which in the closed state defines a laterally open hollow mold space, wherein the inner pressure increases only slightly during baking, the baking mold is kept closed by the inherent weight of the respective tong half lying over the hollow mold space, or by a stationary closing mechanism, which prevents the tong halves of a baking tongs passing by from being moved apart.
Baking tongs whose tong halves contain the mold halves of baking molds which in the closed state define a hollow mold space which is laterally limited all around by sealing strips, wherein the inner pressure increases strongly during baking, are kept closed laterally on two opposite sides of the respective baking tong. In the case of tong halves linked by an articulation, on the side of the baking tong opposite to the articulation a baking tong lock is provided, which is securely locked when the baking tongs is closed. In baking tongs without articulations, whose tong halves are rectilinearly moved towards and away from each other for opening and closing the baking mold, on each of two opposite sides of the baking tong a baking tong lock is provided, which is securely locked when the baking tongs is closed. Each baking tong lock is a mechanism built into the respective baking tong, which is externally actuated when the baking tongs is closed, which in the locked state rigidly connects the two tong halves. Each baking tong lock has to be actuated after the closing of the baking tong and prior to the opening of the baking tongs.
In the known baking ovens, in the baking tongs, respectively in their baking tong halves, flat baking plates are integrated, which are formed on the frontal side as upper or lower mold halves of the baking molds and are heated on their rear side.
From the point of view of construction, layout and function, from the loading station via the individual baking molds and the revolving baking tongs containing the same, to the stationary control mechanisms causing the motions of the individual parts of the revolving baking tongs and to the discharge station for the thin-walled shaped bodies, the known longitudinally extending baking ovens with their continuously revolving baking tong chains are specifically set up exclusively for the production of thin-walled shaped bodies having a single predetermined configuration from shapeless masses prepared according to a certain recipe.
Such baking ovens are used for the industrial production of edible wafers, which are baked in the revolving baking molds of the baking tongs from fluid wafer doughs, which consist primarily of wheat flour and water. Depending on the baking oven and the wafer dough, the consistency of the produced wafers can be crisp, crunchy and brittle wafers, with a moisture content of maximum 1%-4%, or they can have the consistency of soft, elastic wafers with a moisture content of 8% or more.
Such baking ovens are also used for the industrial production of flat decomposable packaging trays, which are baked in the revolving baking molds of the baking tongs from pourable starch-based shapeless masses and which have an elastic consistency with a moisture content of 6% to 22%.
The known longitudinally extending baking ovens with their endless baking tong chains comprising 18 to 140 baking tongs are mechanically very cumbersome machines. The baking molds are received in the baking tongs composed of several components and run through the baking space on lateral running wheels in lateral guide rails on both transport levels of the baking oven. In the antechamber along the guide path of the baking tongs, control cams and mechanisms produce the motions of the tong halves for the opening and closing of the baking molds and the motions of the locking elements of the baking tong locks for locking and unlocking of the closed baking tong. Mechanically cumbersome is also the endless baking tong chain, for which a pneumatic or hydraulic chain-tensioning device mounted on the oven frame is required, and which in addition to the baking tongs also consist of two lateral transport chains, which interconnect the baking tongs and run over chain guides arranged at both ends of the baking oven.
In the known longitudinally extending baking ovens for the production of thin-walled shaped bodies the difference in the production capacity of thin-walled shaped bodies determined by the number of its baking tongs, or baking molds, shows up only in the differences in the length of the baking ovens or their baking spaces. When an existing longitudinally extending wafer baking oven has to be replaced by a new longitudinally extending baking oven with a higher capacity, then at the site of the baking oven a longer construction space is required for the new baking oven. Under limited space conditions, the length available at the site becomes very quickly a limiting factor for any further capacity increase of the longitudinally extending baking oven and the production installations connected thereto for the further treatment and processing of the thin-walled shaped bodies up to the packaging machine for the end product produced from the thin-walled shaped bodies, which is provided at the end of the respective production installation.
From German Patent 714 019 a wafer baking machine is known wherein wafer molded boxes are guided in the side walls of the machine by lateral running rollers. The wafer mold boxes at their top and bottom sides have depressions corresponding to the pattern of the upper or lower side of the wafer to be produced, each carrying lateral hook catches projecting downwards beyond the lower side and thereto assigned locking pins close to their upper side. In a lower transport level, these molding boxes are filled with a baking mass at their upper side and continuously assembled into baking molds at the lower end of a molding box stack supported on stationary catches and extending through a vertical baking shaft upwards to an upper removal station for the baked wafers, each of them consisting of two superimposed molding boxes, rigidly connected by means of the hook catches of the upper box fastened to the locking pins of the lower box. At the lower end of the baking shaft each time a molding box filled with baking mass at its upper side is pressed from below into the baking shaft by means of a crank of a connecting rod gear and joined together with the lowest molding box of the molding box stack to form a baking mold. Thereby the entire molding box stack is lifted by the stationary catches, and lifted by one molding box height, whereby the hook catches of the lowermost molding box in the stack lock into the locking pins of the newly arrived molding box, and then the entire stack with its newest lowermost molding box is again deposited on the stationary catches. With each addition of a molding box at the lower end of the stack, the baking molds in the stack travel stepwise upwards through the baking shaft, while wafers are baked in the baking molds formed by them. When the stack is lifted, in the uppermost baking mold of the stack the hook catches of the upper molding box are swung away from the locking pins of the underlying molding box and the uppermost molding box is coupled to the two endless link chains of an endless conveyor running in the side walls of the machine frame, which lifts this molding box by releasing the uppermost baking mold from the molding box stack and transports it through an upper transport level and a rear vertical transport stretch into the lower transport level, back to the lower end of the baking shaft, where this molding box is again uncoupled from the link chain of the endless conveyor. When the uppermost molding box is lifted from the stack, the baked wafer is left lying on the upper side of the underlying molding box and is removed from this molding box in the upper removal station by means of a stripper. This wafer baking machine has short baking shaft with a low molding box stack, which consists of a few, relatively thin-walled molding boxes, which are rigidly interconnected by means of hook catches and locking pins, in order to be able to withstand the high inner pressures occurring during the baking of the wafers in the baking molds formed by the molding boxes.